A robotic lawnmower is a device configured to autonomously move across a lawn to cut grass by means of a rotating cutting blade. The robotic lawnmower comprises a chassis to which ground engaging wheels and the cutting blade are attached. The robotic lawnmower further comprises a body arranged above the chassis. A function of the body is to prevent people from being injured by the cutting blade, as well as to protect the chassis and cutting blade from rain, dirt and clippings which may cause clogging and malfunction of the robotic lawnmower.
The body may be flexibly attached relative the body in the travelling plane or collision plane, such that a relative displacement of the body relative the chassis is possible if the body collides with an obstacle. This is to enable the robotic lawnmower to detect the obstacle and move away from it.
For this purpose, the connection between the body and the chassis may be arranged to allow relative movement between the body and the chassis in the collision plane, i.e. in a plane essentially parallel to the lawn that is being cut.
A further feature of the robotic lawnmower is an arrangement for lift detection.
This is important for protecting people from being injured by the cutting blade when the robotic lawnmower is lifted during operation, and lift detection arrangements are therefore usually arranged to automatically stop rotation of the cutting blade when a lift is detected.
By having a lift detection arrangement for detecting a lift of the body relative the chassis, it is possible to quickly stop rotation of the cutting blade. Such detection requires a connection of the body to the chassis which allows flexibility in a lift direction.
A problem is that it is difficult to distinguish a lift from a collision, since both lifts and collisions cause the body to flex relative the chassis.
This may cause false lift detections and unnecessary stops of the robotic lawnmower.